/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_shift_q31.c
*
* Description:	Shifts the elements of a Q31 vector by a specified number of bits.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupMath
 */
/**
 * @defgroup shift Vector Shift
 *
 * Shifts the elements of a fixed-point vector by a specified number of bits.
 * There are separate functions for Q7, Q15, and Q31 data types.
 * The underlying algorithm used is:
 *
 * <pre>
 *     pDst[n] = pSrc[n] << shift,   0 <= n < blockSize.
 * </pre>
 *
 * If <code>shift</code> is positive then the elements of the vector are shifted to the left.
 * If <code>shift</code> is negative then the elements of the vector are shifted to the right.
 */

/**
 * @addtogroup shift
 * @{
 */

/**
 * @brief  Shifts the elements of a Q31 vector a specified number of bits.
 * @param[in]  *pSrc points to the input vector
 * @param[in]  shiftBits number of bits to shift.  A positive value shifts left; a negative value shifts right.
 * @param[out]  *pDst points to the output vector
 * @param[in]  blockSize number of samples in the vector
 * @return none.
 *
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function uses saturating arithmetic.
 * Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated.
 */

void arm_shift_q31(
    q31_t* pSrc,
    int8_t shiftBits,
    q31_t* pDst,
    uint32_t blockSize)
{
	uint32_t blkCnt;                               /* loop counter */
	uint8_t sign = (shiftBits & 0x80);             /* Sign of shiftBits */

#ifndef ARM_MATH_CM0

	q31_t in1, in2, in3, in4;                      /* Temporary input variables */
	q31_t out1, out2, out3, out4;                  /* Temporary output variables */

	/*loop Unrolling */
	blkCnt = blockSize >> 2u;


	if(sign == 0u) {
		/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
		 ** a second loop below computes the remaining 1 to 3 samples. */
		while(blkCnt > 0u) {
			/* C = A  << shiftBits */
			/* Shift the input and then store the results in the destination buffer. */
			in1 = *pSrc;
			in2 = *(pSrc + 1);
			out1 = in1 << shiftBits;
			in3 = *(pSrc + 2);
			out2 = in2 << shiftBits;
			in4 = *(pSrc + 3);

			if(in1 != (out1 >> shiftBits))
				out1 = 0x7FFFFFFF ^ (in1 >> 31);

			if(in2 != (out2 >> shiftBits))
				out2 = 0x7FFFFFFF ^ (in2 >> 31);

			*pDst = out1;
			out3 = in3 << shiftBits;
			*(pDst + 1) = out2;
			out4 = in4 << shiftBits;

			if(in3 != (out3 >> shiftBits))
				out3 = 0x7FFFFFFF ^ (in3 >> 31);

			if(in4 != (out4 >> shiftBits))
				out4 = 0x7FFFFFFF ^ (in4 >> 31);

			*(pDst + 2) = out3;
			*(pDst + 3) = out4;

			/* Update destination pointer to process next sampels */
			pSrc += 4u;
			pDst += 4u;

			/* Decrement the loop counter */
			blkCnt--;
		}
	} else {

		/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
		 ** a second loop below computes the remaining 1 to 3 samples. */
		while(blkCnt > 0u) {
			/* C = A >>  shiftBits */
			/* Shift the input and then store the results in the destination buffer. */
			in1 = *pSrc;
			in2 = *(pSrc + 1);
			in3 = *(pSrc + 2);
			in4 = *(pSrc + 3);

			*pDst = (in1 >> -shiftBits);
			*(pDst + 1) = (in2 >> -shiftBits);
			*(pDst + 2) = (in3 >> -shiftBits);
			*(pDst + 3) = (in4 >> -shiftBits);


			pSrc += 4u;
			pDst += 4u;

			blkCnt--;
		}

	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x4u;

#else

	/* Run the below code for Cortex-M0 */


	/* Initialize blkCnt with number of samples */
	blkCnt = blockSize;

#endif /* #ifndef ARM_MATH_CM0 */


	while(blkCnt > 0u) {
		/* C = A (>> or <<) shiftBits */
		/* Shift the input and then store the result in the destination buffer. */
		*pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
		          (*pSrc++ >> -shiftBits);

		/* Decrement the loop counter */
		blkCnt--;
	}


}

/**
 * @} end of shift group
 */
